i havent bought any modem yet,
iam thinking of buying a adsl modem and a network switch without buying a router as my previous router burnt unexpectedly.
If the ADSL modem has only a single ethernet port, chances are it doesn't have a built-in router and it expects to be connected to a single MAC device. Using a simple switch would not work in such a circumstance because a switch doesn't have a MAC address and the model would receive call from multiple computer's MAC; you would need a router for that.
Good to know. Here in Quebec, all major ISP provide the modem and none of them support routing, they are simply gateways. To help the OP, maybe people could contribute a list of DSL modems that have built-in router. After that the OP will be able to decide which solution he prefers (modem/router + switch vs modem+switch).